1. Field of the Invention
The present invention relates to a radio communication apparatus, method and program for burst transmission in a packet communication system, and more particularly to a radio communication apparatus, method and program for determining transmission rate in accordance with radio signal propagation conditions.
2. Description of the Related Art
In many packet communication systems including IEEE 802.11 wireless LANs, data communication can be performed by selecting a supported transmission rate according to, for example, propagation conditions. To determine or change the transmission rate, quality information about the received signal at a destination apparatus, such as the received-signal intensity (RSSI) or signal-to-noise ratio (SNR), and/or whether an acknowledgement (ACK) signal is received from the destination apparatus, is utilized (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 2003-51781).
In IEEE 802.11 wireless LANs, when data is burst-transmitted, as in the case of using the IEEE 802.11e Block Ack function, which is designed to enhance the function of the MAC layer, the conventional transmission rate determination/change method may raise the following problem.
When using received-signal quality information from a destination to determine transmission rate, the determined transmission rate is not always viable since the received-signal quality continuously varies because of such factors as fading. Moreover, if burst transmission is performed at the transmission rate determined from the received-signal quality information, the transmission rate cannot be changed since it cannot be determined during burst transmission whether received-signal quality information or ACK signal is received. Therefore, if the determined transmission rate is not viable, the transmission rate during burst transmission cannot be, for example, reduced, which inevitably increases retransmission and reduces throughput. At worst, communication may be completely interrupted because the number of retransmissions exceeds the maximum allowable.